Differential filtration studies of carbon flux from living algae to microheterotrophs, microplankton size distribution and respiration in Lake Kinneret

Publisher Website
Google Scholar
Abstract
The flux of newly photosynthetically fixed, dissolved organic carbon (PDOC) from phototrophs to microheterotrophs in Lake Kinneret was examined by differential (3 and 0.4μm) filtration after samples were incubated with14C-bicarbonate for 3 hours (in the light) and subsequently for 21 hours (in darkness). Only a small proportion (average about 10%) of the carbon fixed from14C-bicarbonate in the light was associated with particulate matter 3μm) organisms after the dark period, suggesting that the amount of PDOC taken up by unclumped, single bacteria (μm) was not very great. Respiration rates, estimated by the decrease in14C particulate counts in the dark period, ranged from 3.4 to 21.2% of daylight net photosynthesis. In almost all cases, parallel experiments with additions of radioactive glucose or amino acids indicated that the majority of active heterotrophs passed through 3μm filters. Apparent residence times for glucose and amino acids were 20 to 168 hours and 20 to 152 hours, respectively.